Monepantel-based anthelmintic combinations to optimize parasite control in cattle

Abstract

The work described here is complementary to our previous contribution to the characterization of monepantel (MNP) pharmacology in cattle. MNP was given alone or co-administered with either macrocyclic lactones or benzimidazoles to calves naturally infected with multiple-resistant gastrointestinal nematodes (GIN) on two commercial cattle farms. Both, pharmacokinetic(PK) and efficacy assessments were performed. In Farm A, two groups(n= 15) of male calves were treated with either MNP orally (2.5 mg/kg) or IVM subcutaneously (sc, 0.2 mg/kg). In Farm B, eight groups (n=15) of male calves were treated with MNP, IVM, abamectin (ABA, oral, 0.2 mg/kg), ricobendazole (RBZ, sc, 3.75 mg/kg), albendazole (ABZ, oral, 5 mg/kg), MNP+ABA, MNP+RBZ and MNP+ABZ (all at the mentioned doses). Seven animals from each treated group (Farm B) were randomly selected to perform the PK study. MNP and its metabolite monepantel sulphone(MNPSO2) were the main analytes recovered in plasma. Higher Cmax and AUC values were obtained for the active MNPSO2 metabolite compared to MNP. Efficacies of 99%(Farm A) and 96%(Farm B) demonstrated the high efficacy of MNP(P< 0.05) against GIN resistant to IVM in cattle. While IVM failed to control Haemonchus spp. and Cooperia spp., MNP achieved 100% efficacy against Haemonchus spp., Cooperia spp. and Ostertagia spp. on both commercial farms. However, on both farms MNP alone failed to control Oesophagostomum spp.(efficacies ranging from 22 to 74%), increasing up to 99% when MNP was combined with ABA(Farm B). The combined treatments MNP+ABZ and MNP+RBZ reached a 100% reduction against all nematode genera. In conclusion, the oral treatment with MNP should be considered for dealing with multiple-resistant parasites in cattle. Moreover, the use of MNP in combination with benzimidazole compounds could be a valid strategy for improving its poor efficacy against Oesophagostomum spp. The prudent combined use of MNP in cattle may be relevant for extending its lifespan.